HYPOXIA

Hypoxia is O₂ deficiency at the tissue level. Traditionally, hypoxia has been divided into four types.
Numerous other classifications have been used, but the four type system is the one which is most widely used and excepted:

HYPOXIC HYPOXIA

Most common type. A problem seen in NORMAL individuals at HIGH ALTITUDE, complication of PNEUMONIA and many RESPIRATORY COMPLICATIONS. It is a is a condition of reduced arterial pO₂

Low arterial pO₂

Arterio-venous pO₂ difference – LOW

Ventilation – perfusion Imbalance

Venous to arterial Shunt

TREATMENT -Treat the cause. OXYGEN THERAPY

ANAEMIC HYPOXIA

limited ability to deliver O₂ to the active tissues. In anemia hypoxia is seen during exercise. Carbon monoxide poisoning – carboxyhemoglobin/COHb, is formed which shifts available HbO₂ curve to left and CO has 210 times affinity to Hb than O₂ which makes release of CO very slow.

Arterial pO₂ normal

Arterio-venous pO₂ difference – NORMAL

TREATMENT – Hyperbaric OXYGEN therapy

STAGNANT HYPOXIA

Due to slow circulation and is a problem in organs such as the kidneys and heart OR during shock. The liver and possibly the brain are damaged by hypo perfusion during CONGESTIVE HEART FAILURE.

↑  pCO₂ at tissue.

Arterio-venous pO₂ difference – INCREASED

TREATMENT – Treat the underlying cause.

HISTOTOXIC HYPOXIA

Due to inhibition of tissue oxidative processes. CAUSE – cyanide poisoning. Cyanide inhibits cytochrome oxidase and possibly other enzymes at TISSUE level. O₂ utilization is inhibited.

Tissue cant utilize pO₂

Arterio-venous pO₂ difference – ABSENT/ALMOST NIL

TREATMENT – Methylene blue or nitrites are used to treat cyanide poisoning. They act by forming methemoglobin, which then reacts with cyanide to form cyanmethemoglobin, a nontoxic compound.

HYPERBARIC Oxygen

Administration of oxygen-rich gas mixtures is of very limited value in hypoperfusion/Stagnant, anemic, and histotoxic hypoxia. Hyperbaric Oxygen helps by increasing the fraction of DISSOLVED Oxygen. Except SHUNT, in other forms of hypoxic hypoxia, O₂ is of great benefit.

EFFECT OF HYPOXIA

HAPPY HYPOXIA/HYPOXAEMIA IN COVID-19

COVID -19 infection can bring down the Oxygen saturation, as low as 40 %.

Hypoxia is a warning signal for imminent failure of vital body organs like the kidneys, brain, heart and is usually accompanied by prominent breathlessness. Many patients with pronounced arterial hypoxemia don’t even experience a sense of dyspnea. As a result, in the initial stages of sickness, the COVID-19 patient, on the outside, appears to be alright and “happy” due to lack of any external signals.

The trick to life is to just keep breathing. – Johnny Lung